Oxidation of uranosic oxide to uranium



. acid vapors.

2,735,745 Patented Feb. 21, 1956 OXIDATION OF URANOSIC OXIDE T URANIUMTRIOXIDE WITH NITRIC ACHD VAPOR Edward R. Floolr and Roger G. Sweet,Kenmore, N. Y., assignors to the United States of America as representedby the United States Atomic Energy Commission No Drawing. ApplicationJanuary 29, 1948, Serial No. 5,196

1 Claim. (Cl. 23 14.5)

This invention relates to a method for of uranium trioxide (U03), methodfor the preparation uranosic oxide (U308)- An object of this inventionis to provide a method whereby a trioxide of uranium is prepared fromuranosic oxide (U308)- A further object of this invention is to providea method whereby uranosic oxide (U308) is converted to uranium trioxideby a process of oxidation.

According to the process of this invention uranosic oxide (U308) isconverted to uranium trioxide by oxidation with nitric acid vapor.Conversion of uranosic oxide (U308) to the trioxide by this method is animportant step in the production of fluorine-free uranium tri oxide fromthe uranosic oxlde produced by processes such as the pyrohydrolysis ofuranium hexafiuoride and uranyl fluoride. Furthermore, the process ofthis invenfor incorporation in processes involvthe preparation and moreparticularly to a of uranium trioxide from used for the evaporation andhydrolysis of the uranyl fluoride. In this manner dusting and consequentlosses of material are avoided.

In accordance with the Under these conditions the uranosic oxide (U308)is completely converted to uranium trioxide by heating in the presenceof nitric acid vapor to temperatures between 200500 C. Although theconversion of uranosic oxide to the trioxide is complete at 500 C., theuranium trioxide (U03) thus formed is partially degraded to uranosicoxide (U308) unless the material is cooled in the continued presence ofnitric acid vapors to temperatures below 400" C. At temperatures between200320 C. the product is caked and not very friable, while attemperatures above 400 C. the rate of oxidation is quite slow. It istherefore readily apparent that temperatures between 300400' C. are themore suitable, while those temperatures in the vicinity of 350 sinceoxidation takes substantially pure uranium trioxide and contains notmore than 0.02% tetravalent uranium as U02 and less than 0.0015fluorine. Being soft and friable the product is easily handled duringprocessing, since it does not stick to the reaction vessel and it iseasily broken up to powder form merely by agitation.

The uranosic oxide (U308) is oxidized to uranium trioxide by vaporsconsisting of a mixture of HN03, N0, N02, 02, and

solution (ca. 68.3% HNOa), is passed over the uranosic oxide (U308),which is heated in the manner previously described. While the uranosicoxide (U308) is thus heated, the vapor from the constant boiling nitricacid solution is passed over at a rate suflicient to permit onlycolorless vapors to come in contact with the reactant When the vaporflow is decreased to the extent that the reaction vessel is filled withfumes having a brown color, the conversion to uranium trioxide is lesscomplete.

The following vapor, the exposed surface area of the reactive mass, thereaction temperature.

Example I A layer (%-inch deep) of uranosic oxide (UaOa), weighing 300g.

Vapors from 750 ml. of a constant-boiling nitric acid solution (68.3%HNO3) were passed over the oxide for one hour and Example II C. for twoand one-fourth hours with the vapor derlved from 250 ml. of aconstant-boiling nitric acid solution. Conversion to uranium trioxideWas substantially complete. The fluorine content of the uranium trioxidethus produced was less than 0.0015% and the percent U02 in the productwas 0.02.

The foregoing examples this invention, of which there are numerousmodifications which are readily apparent to those skilled in the art.

What is claimed is: A process for the oxidation of uranosic oxide touranium trioxide, comprising heating uranosic oxide at a temperaturebetween 400500 C. in the presence of References Cited in the tile ofthis patent Sabatier et al.: Comptes Rendus, vol. 114, page 1431 (1892);vol. 120, pages 618-20 (1895).

Babor et al.: General College Chemistry, 2nd edition, page 390; pub. in1940 by Thos. Y. Crowell Co., New York.

Mellor: Inorganic and Theoretical Chemistry, vol. 8, page 583; pub. in1928 by Longmans, Green and Co., London; vol. 12, page 54, pub. in 1932.

